I am using a pin without any external capacitors and I can see the clock coming out. The only problem is that the slew-rate is very bad.

I saw in the documentation that the PSOC4 devices has a CLK configuration for the digital output pin, but that is not available for .PSOC 5LP. Is there some other way to increase the slewrate in the current device?

Morten, it is likely an issue with your scope probe. If you using $10 (for pair) probes from Ali, then 60ns slopes is what you will see on 100MHz scope. For standard probes use 10X settings on the probe and 50oHm input impedance on the scope (or add 50oHm BNC load) Alternately make your own 1:20 probe using 1k resistor at the tip of coax cable (google the recepie) and 50oHm BNC load. Using such cables I see ~5ns fronts on PSoC pins